1. Field of the Invention
This invention relates generally to mooring line connections for subsea operations, particularly for suction anchor pile moorings. More particularly, this invention concerns a wire socket connector mechanism which facilitates subsea connection and reconnection of mooring lines of semi-submersible drilling rigs, production and drilling platforms and the like to suction anchor piles and other anchor devices. This invention also concerns deployment and installation of suction anchor piles and a mooring wire assembly with retrieval buoys and sling on one of its ends. The invention also concerns addition of buoys to mooring wire sections and connecting the mooring wire to a vessel to be moored. The procedure also concerns the mooring wire, buoy recovery, wire retrieval and suction anchor pile recovery and a procedure for recovering mooring wires and other apparatus.
2. Description of the Prior Art
Present procedures for installing subsurface anchors and establishing mooring the connection between the anchors and a semisubmersible drilling rig has required the presence of two service vessels, one an anchor handling vessel equipped with an A-frame type hoist for transporting the anchor and for lifting the anchor. The second service vessel is used to pull the hoisted anchor from the anchor handling vessel and to assist the anchor handling vessel in deployment of the anchor. When a large A-frame type hoisting mechanism is utilized for lifting the anchor from the anchor handling vessel, particularly in rough sea conditions, the heavy and bulky anchor and its peripheral equipment may swing to and from and may strike and damage other equipment in the immediate vicinity of the A-frame type hoisting mechanism. Additionally, since personnel will typically be required to ascend the A-frame type hoisting mechanism, such as to string wire rope and conduct other activities, the heavy swinging load of an anchor that is supported by the hoist constitutes and the movement of the A-frame hoist along with the vessel present significant hazards to the safety of workers whether present on the deck of the vessel or on the A-frame hoist or in the rigging of the hoist. It is desirable therefore to provide a system for transportation and deployment of subsea anchors and mooring lines which does not constitute a safety hazard for workers. It is also desirable to provide a system for transportation and deployment of subsea anchors and mooring lines and which minimizes the potential for damage to the vessel and its equipment even under circumstances where the sea conditions are rough during anchor deployment and recovery and during deployment and recovery of mooring lines. It is also desirable to provide a system for the handling, deployment and recovery of subsea anchors and installation and recovery of mooring lines which effectively minimizes the cost of stationing and mooring a semisubmersible vessel such as a drilling rig for well drilling operations.
Another significant disadvantage of using two service vessels for anchor transportation, handling and deployment is simply the duplication of costs when two vessels are utilized rather than a single vessel. It is desirable therefore to provide a system, utilizing a single anchor handling vessel, which is capable of transporting, deploying and retrieving subsea anchors in deep water conditions and is also capable of accomplishing connection and disconnection of mooring lines to permit drilling vessels to be quickly and efficiently stationed and restationed, thus conserving not only service vessel time and consequent cost but also conserving drilling vessel time and consequent cost.
The common feature of the present invention is the installation of a mooring anchor without the mooring line attached at the time of deployment and embedment in the sea bottom. Prior to the invention of the subsea connector shown in FIGS. 21-25 hereof it was not possible to install an anchor in deeper water without the mooring line being attached to the anchor at the time of deployment. Heretofore, there has been no practical means of connecting a mooring line to an anchor embedded in the sea bottom in water depths that could not be manually accessed.
There is considerable advantage in being able to install mooring anchors without the mooring line attached. Several styles of advanced high holding power anchors for use in deeper water depths need to be deployed and embedded with a deployment line that has an attachment point apart from the preferred point of attachment of the mooring line. Previously, it had been necessary to deploy such anchors with both a deployment line extending from the principal deployment vessel and a separate mooring line extending from a second deployment vessel in order to prevent the two lines from becoming entangled with one another. The requirement for the use of two anchor handling and deployment vessels has added considerable cost and logistical difficulty to the anchor and mooring system deployment process. The method of mooring set forth herein is designed to specifically avoid this difficulty. In vessel anchoring situations such as is disclosed in U.S. Pat. No. 4,347,012 of Glidden the basic anchor base structure xe2x80x9cAxe2x80x9d must be deployed and installed at the sea bed with the pull line xe2x80x9cPxe2x80x9d attached or by threading the pull line P about the pulleys 18 and 19 and through the side opening 25 after the anchor base has been installed. While this activity can be accomplished in shallow water conditions, such as by a diver, it cannot be accomplished when water depth exceeds the working depth of divers. Thus, for deep water anchor deployment and installation, the anchor system of Glidden would require the use to two vessels, one vessel to handle the anchor base and another vessel to manipulate the pull line and prevent rotation of the anchor base due to cable unwinding during deployment and to thus keep the pull line from tangling with the anchor deployment line. The present invention is designed to promote anchor deployment with a single anchor handling and without any line being attached other than the anchor deployment line. Consequently, wound cable may be used for anchor deployment and anchor rotation by cable unwinding during deployment does not detract from the deployment procedure, since no cable fouling can be caused by anchor rotation. The present invention permits efficient single vessel, single line anchor deployment and also facilitates simple and efficient deployment line disconnection and mooring line connection via the use of ROVs. Later, when vessel mooring is no longer needed, the present invention also facilitates mooring line disconnection and anchor retrieval, again through the use of a single vessel and a single lifting line which permits rotation of the anchor during recovery from the sea bed.
There are several principal features of the mooring method of the present invention that prove to be practical and advantageous, the most simple of which is the deployment of the anchor with a single line from a single vessel with no mooring line attached as shown in FIGS. 14 and 15. Once the anchor is embedded, the mooring line is attached as shown in FIG. 16 by the same or another vessel and laid on the sea bed or attached to a buoy which can be retrieved later, or the mooring line is attached to the anchor at some later date. This method provides the most efficient installation of the anchor and the most flexible arrangement for mooring line attachment to the anchor and connection to the marine structure to be moored.
The present invention envisions the use of Remote Operated Vehicles, called ROV""s to operate the connector that connects the mooring line to the installed anchor. In fact, the connector is specifically designed to handle the mooring loads and be operated by the ROV. As such, the connector is a unique invention and this method of mooring that it enables is also a unique invention.
It is a principal feature of the present invention to provide a novel system for anchor transportation, handling deployment and recovery which is accomplished by a single anchor handling vessel.
It is also desirable to provide a system for anchor transportation, handling deployment and recovery and which enables a plurality of subsea anchors to be simultaneously transported and permits the anchors to be individually deployed and recovered even under conditions of rough seas.
It is another feature of the present invention to provide a novel system for anchor transportation, handling, deployment and recovery wherein the anchors, particularly suction piles, are moved over the stem roller of a single anchor handling vessel during deployment and retrieval operations.
It is an even further feature of the present invention to provide a novel system for anchor transportation, handling, deployment and recovery which facilitates a unique single vessel handling system enabling anchor connections and disconnections with a minimum of expended time and with a minimum of cost.
The common feature of the present invention is the installation of a mooring anchor without the mooring line attached at the time of deployment and embedment in the sea bottom. Prior to the invention of the subsea connector shown in FIGS. 21-25 hereof it was not possible to install an anchor in deeper water without the mooring line being attached to the anchor at the time of deployment. Heretofore, there has been no practical means of connecting a mooring line to an anchor embedded in the sea bottom in water depths that could not be manually accessed.
There is considerable advantage in being able to install mooring anchors without the mooring line attached. Several styles of advanced high holding power anchors for use in deeper water depths need to be deployed and embedded with a deployment line that has an attachment point apart from the preferred point of attachment of the mooring line. Previously, it had been necessary to deploy such anchors with both a deployment line extending from the principal deployment vessel and a separate mooring line extending from a second deployment vessel in order to prevent the two lines from becoming entangled with one another. The requirement for the use of two anchor handling and deployment vessels has added considerable cost and logistical difficulty to the anchor and mooring system deployment process. The method of mooring set forth herein is designed to specifically avoid this difficulty. In vessel anchoring situations such as is disclosed in U.S. Pat. No. 4,347,012 of Glidden the basic anchor base structure xe2x80x9cAxe2x80x9d must be deployed and installed at the sea bed with the pull line xe2x80x9cPxe2x80x9d attached or by threading the pull line P about the pulleys 18 and 19 and through the side opening 25 after the anchor base has been installed. While this activity can be accomplished in shallow water conditions, such as by a diver, it cannot be accomplished when water depth exceeds the working depth of divers. Thus, for deep water anchor deployment and installation, the anchor system of Glidden would require the use to two vessels, one vessel to handle the anchor base and another vessel to manipulate the pull line and prevent rotation of the anchor base due to cable unwinding during deployment and to thus keep the pull line from tangling with the anchor deployment line. The present invention is designed to promote anchor deployment with a single anchor handling and without any line being attached other than the anchor deployment line. Consequently, wound cable may be used for anchor deployment and anchor rotation by cable unwinding during deployment does not detract from the deployment procedure, since no cable fouling can be caused by anchor rotation. The present invention permits efficient single vessel, single line anchor deployment and also facilitates simple and efficient deployment line disconnection and mooring line connection via the use of ROVs. Later, when vessel mooring is no longer needed, the present invention also facilitates mooring line disconnection and anchor retrieval, again through the use of a single vessel and a single lifting line which permits rotation of the anchor during recovery from the sea bed.
There are several principal features of the mooring method of the present invention that prove to be practical and advantageous, the most simple of which is the deployment of the anchor with a single line from a single vessel with no mooring line attached as shown in FIGS. 14 and 15. Once the anchor is embedded, the mooring line is attached as shown in FIG. 16 by the same or another vessel and laid on the sea bed or attached to a buoy which can be retrieved later, or the mooring line is attached to the anchor at some later date. This method provides the most efficient installation of the anchor and the most flexible arrangement for mooring line attachment to the anchor and connection to the marine structure to be moored.
The present invention envisions the use of Remote Operated Vehicles, called ROV""s to operate the connector that connects the mooring line to the installed anchor. In fact, the connector is specifically designed to handle the mooring loads and be operated by the ROV. As such, the connector is a unique invention and this method of mooring that it enables is also a unique invention.
Briefly, the various objects and features of the present invention are realized by providing an anchor handling vessel which is equipped to mount a plurality of subsea anchors along the sides of the deck, leaving the central part of the deck for anchor handling. The vessel is equipped with a track mechanism which is used to move a selected anchor laterally from its tethered position along a side of the vessel and to position the anchor in substantial alignment with the longitudinal centerline of the vessel deck. The track mechanism is also operated to move the selected anchor linearly toward the stem roller of the vessel and to launch the anchor over the stem roller so that it is suspended by a support and handling line or lines. The suction pile type anchor is lowered to its desired position and installed in conventional manner. The anchor handling line may be utilized as a section of the mooring line, in which case its connection for lifting and supporting the anchor is released and the line is moved to a mooring connection of the anchor and reconnected. A remote operating vehicle (ROV) may be used for this purpose or a remotely operated quick-release connector may be utilized to release the anchor support and handling connection and to establish the mooring connection.